A picture taken on December 3, 2015 shows "wind trees", a renewable energy innovation constructed in the shape of a tree, where each "leaf" acts as a mini wind-turbine to generate electricity, displayed at the COP21, the United Nations conference on climate at Le Bourget, on the outskirts of Paris. More than 150 world leaders are meeting under heightened security, for the 21st Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change (COP21/CMP11), als

Negotiators charged with saving humanity from a climate catastrophe on Thursday unveiled a new draft deal riddled with conflicting proposals after three days of talks in Paris, sparking deep concern among activists.

The UN talks being attended by representatives of 195 nations north of Paris aim to slash greenhouse-gas emissions which trap the Sun's heat, warming Earth's surface and oceans and disrupting its delicate climate system.

Taking effect from 2020, the pact would target emissions from fossil fuels such as coal, oil and gas -- the backbone of the world's energy supply today -- and channel hundreds of billions of dollars in climate aid to vulnerable countries.

More than 150 world leaders including President Barack Obama launched the talks Monday, seeking to build momentum for the tough negotiations ahead with lofty rhetoric about the urgency of the task.

But after three days of grinding discussions over a hugely complex 54-page draft pact, bureaucrats unveiled a document just four pages shorter and with vast stretches of text yet to be agreed.

Ministers from around the globe will descend on Paris Monday to try to transform the draft prepared by diplomats into a universal climate accord to avert planetary overheating. The conference is scheduled to conclude on December 11.

"At this rate, when ministers arrive next week they will wonder what progress has been made since world leaders took to the podium in Paris," said Greenpeace's head of international climate politics Martin Kaiser.

'Better view of the iceberg'

At the core of the talks is the goal of limiting average warming to a maximum of two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.

Kaiser said long-term goals were now clearer in the draft, though it did not call for fossil fuels to be phased out by 2050 so as to limit warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) -- a more ambitious target being pushed by low-lying island nations at risk of sinking into rising seas.

"On other parts of the text, there's been even less progress," he warned.

"The negotiators need to find ways of bridging the differences, and soon, so by this time next week they are in the final stretch of this summit with a good chance of agreeing something historic," Kaiser said.

"These negotiations need to switch gear now."

The number of undecided options littering the text -- 250 in total -- remain unchanged, said Matthieu Orphelin, spokesman for French environmental group Fondation Nicolas Hulot.

"We have only got 48 hours. The negotiations have to accelerate," he said.

The World Wide Fund for Nature's head of delegation, Tasneem Essop, said the draft was "mostly unchanged" from when negotiators landed in Paris.

"Right now, they're still just rearranging the deck chairs on the ship to get a better view of the iceberg," it said in a statement.

Nevertheless, she said the text contained the core elements for an accord, and the results could have been worse. "It is good to see that despite some fears the text has not ballooned further with lots of new insertions."

'Failure unthinkable'

Despite the concerns, French Environment Minister Segolene Royal said negotiations were advancing.

"It is normal for it to take a day or two for negotiations to get into gear," she told AFP. "It is unthinkable to imagine failure."

Scientists warn time for action is running out, issuing ever-louder warnings that steadily growing carbon emissions will doom future generations to rising seas and worsening floods, storms and drought -- a recipe for hunger, disease and homelessness for many millions.

Bonn-based climate analysts Germanwatch issued a report saying Honduras, Myanmar and Haiti topped the list of nations hardest hit by two decades of extreme weather events such as storms, floods and landslides that killed more than half a million people.

"The Climate Risk Index thus indicates a level of exposure and vulnerability to extreme events that countries should understand as a warning to be prepared for more frequent and/or more severe events in the future," the report said.